Solar Melanoma

Abstract

Solar melanoma is also called by many lentigo maligna melanoma, melanoma associated with Hutchinson’s melanotic freckle, and lentigo malin des vieillards of Dubreuilh. Originally described by Sir Jonathan Hutchinson, this variant of melanoma is appropriately termed solar melanoma (SM) because its development is directly related to cumulative sunlight exposure (9–11,32,34,55–79) (Table 13). SM are defined by their localization to continuously/chronically sun-exposed skin and the presence of significant solar elastosis histologically. They are also distinctive lesions because of their gross morphologic appearance, characteristic slow evolution, development in elderly individuals, and often distinctive histopathologic appearance. Approximately 4–15% of melanomas occurring in whites are of the solar subtype (22). There some evidence that they are increasing in frequency. They generally affect older individuals with a median age at diagnosis of 65 years for invasive SM. However, they may be observed in younger individuals living in geographic areas with high insolation. There is a predilection for the head and neck, with the cheek being the single most commonly affected site followed by the nose and forehead. Uncommonly they may develop at other sites of chronic sun exposure such as the dorsal surfaces of the hands or lower legs. Often the solar melanomas develop after an indolent period of growth (20–30 years and even up to 50 years) as an atypical intraepidermal melanocytic proliferation (lentigo maligna, Hutchinson melanotic freckle, SIMP) before in situ and invasive melanoma ensues (Table 9; see below).